This is 100% scam and you are not going to get any free T-shirt. Do not click any link if you come across such post on Facebook. You should simply click X button to remove the post from your Facebook wall.

This is a tricky method to hijack your Facebook account and further spread this scam via your Facebook account.

What should I do if I see this scam post from my trusted friend

If you see this scan post by any of your friend, you should alert him about this. Tell him to change his Facebook account password, associated email account password and remove all unwanted Facebook apps.